feat: update Dockerfiles to use explicit image paths and enhance localStorage handling in ThemeService

backend/Dockerfile

@@ -1,5 +1,5 @@
 # Build stage
-FROM maven:3.9-eclipse-temurin-25-alpine AS build
+FROM docker.io/library/maven:3.9-eclipse-temurin-25-alpine AS build
 WORKDIR /app
 COPY pom.xml .
 RUN mvn dependency:go-offline
@@ -7,7 +7,7 @@ COPY src ./src
 RUN mvn clean package -DskipTests
 
 # Run stage
-FROM eclipse-temurin:25-jre
+FROM docker.io/library/eclipse-temurin:25-jre
 WORKDIR /app
 COPY --from=build /app/target/backend-0.0.1-SNAPSHOT.jar app.jar
 EXPOSE 8080